The overall objective is to investigate the structure and function of gag-mos and env-mos proteins encoded by Moloney murine sarcoma virus (MuSV) for the purpose of elucidating the molecular mechanism by which v-mos products produce transformation in viral infected cells. Efforts will be made to compare the transforming potential of the gag-mos proteins to env-mos proteins of Moloney MuSV. Overall, these studies will yield valuable and significant information on the mechanism of transformation by the activated mos gene. It is of special interest that a ts gag-mos gene mutant will be used in these studies. Such mutants are important tools in determining the function on oncogene products. Of prime importance is our discovery that P85gag-mos and p37env-mos have an associated protein kinase activity. Using anti-v-mos peptide sera, we have detected a 55k normal cellular nuclear protein (P55) whose expression is specifically inhibited during acute infection by MuSV. The Specific Aims include: 1) Purify the protein kinase associated with P85gag-mos and/or p37env-mos; 2) Determine whether the bacterially expressed partially purified env-mos protein (50% pure) active in transformation of NIH 3T3 cells following transfection, has protein kinase activity. This work is being done in collaboration with Dr. Arun Seth of George Vande Woude's group at the Frederick Cancer Center; 3) Determine the location of the phosphorylation sites within gag-mos and env-mos proteins and identify their phosphopeptides; 4) Characterize the structure of the P55 protein by peptide mapping and limited amino acid sequencing; 5) Determine the sites of phosphorylation of P55 by the v-mos serine kinase and verify the presence of phosphoserine; 6) Clone the cellular gene for P55 by recombinant DNA techniques; 7) Identify other possible cellular targets of v-mos proteins; 8) Search for c-mos proteins using synthetic peptide antisera; 9) In collaboration with Dr. Steve Reed of the University of California at Santa Barbara, prepare site directed mutants of the v-mos gene coding for p37env-mos.